System, method and apparatus for aligning and synchronizing target material for optimum extreme ultraviolet light output

ABSTRACT

An extreme ultraviolet light system and method includes a drive laser, a chamber including an extreme ultraviolet light collector and a target material dispenser including an adjustable target material outlet capable of outputting multiple portions of target material along a target material path. Also included: a drive laser steering device, a detection system including at least one detector and a controller coupled to the target material dispenser, the detector system and the drive laser steering device. The controller includes logic for detecting a location of the first portion of target material from the first light reflected from the first portion of target material and logic for adjusting the target material dispenser outlet to output a subsequent portion of target material to a waist of the focused drive laser. A system and a method for optimizing an extreme ultraviolet light output is also disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority from U.S. patentapplication Ser. No. 12/725,178 filed on Mar. 16, 2010 and entitledSystem, Method and Apparatus for Aligning and Synchronizing TargetMaterial for Optimum Extreme Ultraviolet Light Output which isincorporated herein by reference for all purposes. This application alsoclaims priority through, U.S. patent application Ser. No. 12/725,178,from U.S. Provisional Patent Application No. 61/168,033 filed on Apr. 9,2009 and entitled “Extreme Ultraviolet Light Output,” which isincorporated herein by reference in its entirety for all purposes. Thisapplication also claims priority from U.S. Provisional PatentApplication No. 61/168,012 filed on Apr. 9, 2009 and entitled “System,Method and Apparatus for Laser Produced Plasma Extreme UltravioletChamber with Hot Walls and Cold Collector Mirror,” which is incorporatedherein by reference in its entirety for all purposes. This applicationalso claims priority from U.S. Provisional Patent Application No.61/168,000 filed on Apr. 9, 2009 and entitled “System, Method andApparatus for Droplet Catcher for Prevention of Backsplash in a EUVGeneration Chamber,” which is incorporated herein by reference in itsentirety for all purposes.

BACKGROUND

The present invention relates generally to laser produced plasma extremeultraviolet systems, methods and apparatus, and more particularly, tosystems, methods and apparatus for droplet management in a laserproduced plasma extreme ultraviolet system.

Laser produced plasma (LPP) extreme ultraviolet (EUV) systems produce aplasma by irradiating a plasma source material (e.g., target material)with a drive laser. The resulting plasma emits light and a desiredwavelength, in this instance, EUV (e.g., less than about 50 nmwavelength).

To produce the optimum power output the drive laser ideally irradiatesthe target material. Unfortunately the drive laser can partially orcompletely miss the target material.

In view of the foregoing, there is a need for providing feedback foroptimally aligning the drive laser to the target material and/oraligning the target material with the drive laser.

SUMMARY

Broadly speaking, the present invention fills these needs by providingan improved system and method for irradiating plasma target material inan optimum location for producing the maximum amount of emitted EUVlight and the collection of the emitted EUV light. It should beappreciated that the present invention can be implemented in numerousways, including as a process, an apparatus, a system, computer readablemedia, or a device. Several inventive embodiments of the presentinvention are described below.

One embodiment provides an extreme ultraviolet light system. The systemincludes a drive laser system, an extreme ultraviolet light chamberincluding an extreme ultraviolet light collector and a target materialdispenser including a target material outlet capable of outputting amultiple portions of target material along a target material path,wherein the target material outlet is adjustable. The extremeultraviolet light system further includes a drive laser steering deviceand a detection system. The detection system includes at least onedetector directed to detect a reflection of the drive laser reflectedfrom the target material. The system further includes a controllercoupled to the target material dispenser, the detector system and thedrive laser steering device. The controller detects a location of afirst target material from a first light reflected from the first targetmaterial and adjusts the target material dispenser outlet to output asubsequent target material to a waist of the focused drive laser. Thecontroller can also adjust a drive laser steering device to translatethe waist of the drive laser with the target material.

The drive laser can be aligned with a light path between the drive laserand the first one of the portions of the target material. The detectionsystem can be substantially in line with the light path and thereflection of the drive laser reflected off of the target material canbe reflected along the light path toward the drive laser.

The drive laser system can also include an output window and thedetection system may not be in line with the light path and thereflection of the drive laser can be reflected off of the targetmaterial and reflected along the light path toward the drive laseroutput window and the reflection of the drive laser can be furtherreflected off of the output window and toward the detection system.

The drive laser steering device can include at least one reflectingsurface. An actuator can be coupled to the at least one reflectingsurface so that the actuator can adjust the position of the at least onereflecting surface. The detector directed to detect light reflected fromthe target material can include a near field detector and/or a far fielddetector.

The drive laser system can include a CO2 laser. The drive laser systemcan include a master oscillator power amplifier configuration laser. Thedrive laser system can include a multi stage amplifier. The outputwindow of the drive laser system can include a ZnSe window or a diamondwindow.

The waist of the focused drive laser is in an XY plane normal to a lightpath of the drive laser along a Z axis in the EUV chamber. The multipleportions of target material can be output along a target material pathand the target material path can form an angle to the XY plane.

Another embodiment provides a method of generating an extremeultraviolet light. The method includes irradiating a first one ofmultiple portions of a target material with a drive laser, detecting afirst light pulse reflected from the first portion of the targetmaterial, determining a location of the first portion of the targetmaterial, adjusting a location of a second one of the multiple portionsof the target material to a waist of a focused drive laser, irradiatingthe second portion of the target material with the drive laser. Thewaist of the focused drive laser can be aligned to the target material.

Detecting the first light pulse reflected from the first portion of thetarget material can include detecting the first light pulse reflectedfrom an output window of the drive laser. Detecting the first lightpulse reflected from the first portion of the target material caninclude determining at least one of a near field profile and/or a farfield profile of the target material. Adjusting the waist of the focuseddrive laser can include adjusting a position of at least one reflectingsurface of the drive laser.

Yet another embodiment provides a method of optimizing an extremeultraviolet light output. The method includes determining an amount ofeach one of a first set of EUV output pulses during a selected timeinterval including for each one of the first set of EUV output pulses:placing a corresponding one of a first set of portions of targetmaterial in a waist of the focused drive laser, directing a focusedlaser pulse on the corresponding portion of target material, measuringan amount of a corresponding EUV output pulse and recording the measuredcorresponding EUV output pulse quantity. Each one of the first set ofEUV output pulses is analyzed and a target material position is adjustedin +Z direction relative to the waist of the focused laser when thegreatest peak EUV amount occurs in a first occurring portion of thefirst plurality of EUV output pulses and the target material position isadjusted in −Z direction relative to the waist of the focused laser whenthe greatest peak EUV amount occurs in a last occurring portion of thefirst plurality of EUV output pulses. An integral is calculated for thefirst set of EUV output pulses during the selected time interval. Atiming of the drive laser and/or the target material can be adjusted toalign the target material and the waist of the focused drive laser inthe Y axis where the Y axis corresponds with a component of the targetmaterial path that is perpendicular to the Z axis. Steering the drivelaser and/or the target material can include adjusting the drive laserand/or the target material to align the drive laser to the targetmaterial in the X axis, where the X axis is perpendicular to both thedrive laser and the path of the target material.

Other aspects and advantages of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be readily understood by the followingdetailed description in conjunction with the accompanying drawings.

FIG. 1 is a schematic view of a laser-produced-plasma EUV light source,in accordance with embodiments of the disclosed subject matter.

FIG. 2A is a schematic of the components of a simplified target materialdispenser that may be used in some or all of the embodiments describedherein in accordance with embodiments of the disclosed subject matter.

FIG. 2B is a more detailed schematics of some of the components in a EUVchamber in accordance with embodiments of the disclosed subject matter.

FIG. 3A is a flowchart diagram that illustrates the method operationsperformed in generating EUV, in accordance with embodiments of thedisclosed subject matter.

FIGS. 3B-E are simplified schematics of the irradiation of a portion oftarget material, in accordance with embodiments of the disclosed subjectmatter.

FIGS. 4A and 4B are more detailed schematics of the light source inaccordance with embodiments of the disclosed subject matter.

FIGS. 4C.1-4C.2 are images of the reflected light reflected frompreliminary droplet(s), in accordance with embodiments of the disclosedsubject matter

FIG. 4D is a simplified schematic of the target material, in accordancewith embodiments of the disclosed subject matter.

FIG. 5A is a flowchart diagram that illustrates the method operationsperformed in generating EUV, in accordance with embodiments of thedisclosed subject matter.

FIG. 5B is a flowchart diagram that illustrates the method operationsperformed in adjusting the position of the waist relative to the targetmaterial, in accordance with embodiments of the disclosed subjectmatter.

FIGS. 6A, 7A and 8A are simplified close up views of the irradiationregion, in accordance with embodiments of the disclosed subject matter.

FIGS. 6B, 7B and 8B are graphical representations of multiple focusedlight pulses corresponding to FIGS. 6A, 7A and 8A, respectively, inaccordance with embodiments of the disclosed subject matter.

FIGS. 6C, 7C and 8C are graphical representations of the resultingmultiple EUV pulses corresponding to the multiple focused light pulsesin FIGS. 6B, 7B and 8B, respectively, in accordance with embodiments ofthe disclosed subject matter.

FIGS. 6D, 7D and 8D are graphical representations of correspondingintegrals of the multiple resulting EUV pulses corresponding to FIGS.6C, 7C and 8C, respectively, in accordance with embodiments of thedisclosed subject matter.

FIG. 9 is a flowchart diagram that illustrates the method operationsperformed in adjusting the position of the waist relative to the targetmaterial to optimize EUV output, in accordance with embodiments of thedisclosed subject matter.

FIG. 10 is a block diagram of an integrated system including the EUVchamber, in accordance with embodiments of the disclosed subject matter.

DETAILED DESCRIPTION

Several exemplary embodiments for an improved system and method forirradiating plasma target material in an optimum location for producingthe maximum amount of emitted EUV light and the collection of theemitted EUV light will now be described. It will be apparent to thoseskilled in the art that the present invention may be practiced withoutsome or all of the specific details set forth herein.

An optimal location of the plasma target material yields a maximum EUVlight output. The optimal location of the plasma target materialincludes several aspects. The drive laser imparts maximum energy to thetarget material by irradiating the target material in a waist of thefocused drive laser. The target material can be slightly offset to oneedge of the waist of the focused laser in a plane normal to the path ofthe laser, where the path of the drive laser into and through the EUVchamber is a Z axis and the plane normal to the Z axis is designated theX-Y plane. To correct for the offset, the target material can bedirected back toward the waist of the focused drive laser and/or thedrive laser can be steered to translate the waist to the target materialpath.

One LPP technique involves generating a stream of plasma target materialand irradiating a portion of the target material with locating laserpulses followed by a main irradiating laser pulse. In more theoreticalterms, LPP light sources generate EUV radiation by depositing light orlaser energy into a target material having at least one EUV emittingelement (e.g., xenon (Xe), tin (Sn) or lithium (Li)), creating a highlyionized plasma with electron temperatures of several 10's of eV. Theenergetic radiation generated during de-excitation and recombination ofthese ions is emitted from the plasma in all directions. The targetmaterial can be in the form of liquid droplets, or solid pellets, or awire coated in and carrying liquid or solid target material, or a tapeor strip of target material or other systems or methods of transportingthe selected target material to the waist of the focused drive laser. Astream of plasma target material droplets is used herein as an exemplaryembodiment only. Other forms of plasma target material can be used insimilar manners as described herein.

In an exemplary arrangement that is currently being developed with thegoal of producing about 100 W at the intermediate focus, a pulsed,focused 10-12 kW CO2 drive laser (or suitable other laser such as anexcimer laser) is synchronized with a target material droplet generatorto sequentially irradiate about 10,000-200,000 target material dropletsper second. This arrangement produces a stable stream of droplets at arelatively high repetition rate (e.g., 10-200 kHz or more) and deliversthe droplets to an irradiation site at or near the primary focus of thecollector mirror with high accuracy and good repeatability in terms oftiming and position over relatively long periods of time.

FIG. 1 is a schematic view of a laser-produced-plasma EUV light source20, in accordance with embodiments of the disclosed subject matter. TheLPP light source 20 includes a light pulse generation system 22 forgenerating a train of light pulses and delivering the light pulses intoa EUV chamber 26. Each light pulse 23 travels along a beam path 21inside a beam transport system 25 from the light pulse generation system22. The light pulse 23 is focused into the EUV chamber 26 to illuminateand/or irradiate a selected target droplet at an irradiation region 28.

Suitable lasers for use in the light pulse generation system 22 shown inFIG. 1, may include a pulsed laser device, e.g., a pulsed gas dischargeCO2 laser device producing radiation at about 9.3 μm or about 10.6 μm,e.g., with DC or RF excitation, operating at relatively high power,e.g., about 10 kW or higher and high pulse repetition rate, e.g., about10 kHz or more. In one particular implementation, the laser in the lightpulse generation system 22 may be an axial-flow RF-pumped CO2 laserhaving a MOPA configuration with multiple stages of amplification andhaving a seed pulse that is initiated by a Q-switched master oscillator(MO) with low energy and high repetition rate, e.g., capable of 100 kHzoperation. From the MO, the laser pulse may then be amplified, shaped,and focused before reaching the irradiation region 28.

Continuously pumped CO2 amplifiers may be used for the light pulsegeneration system 22. For example, a suitable CO2 laser device having anoscillator and multiple amplifiers (e.g., O-PA1-PA2 . . . configuration)is disclosed in co-owned U.S. Pat. No. 7,439,530, issued on Oct. 21,2008, entitled, LPP EUV LIGHT SOURCE DRIVE LASER SYSTEM, the entirecontents of which are hereby incorporated by reference herein.

Alternatively, the laser in the light pulse generation system 22 may beconfigured as a so-called “self-targeting” laser system in which thesurface of the target material in the laser waist serves as one mirrorof the optical cavity. In some “self-targeting” arrangements, a masteroscillator may not be required. Self targeting laser systems aredisclosed and claimed in co-owned U.S. Pat. No. 7,491,954, issued onFeb. 17, 2009, entitled, DRIVE LASER DELIVERY SYSTEMS FOR EUV LIGHTSOURCE, the entire contents of which are hereby incorporated byreference herein.

Depending on the application, other types of lasers may also be suitablefor use in the light pulse generation system 22, e.g., an excimer ormolecular fluorine laser operating at high power and high pulserepetition rate. Other examples include, a solid state laser, e.g.,having a fiber, rod or disk shaped active media, a MOPA configuredexcimer laser system, e.g., as shown in U.S. Pat. Nos. 6,625,191,6,549,551, and 6,567,450, the entire contents of which are herebyincorporated by reference herein, an excimer laser having one or morechambers, e.g., an oscillator chamber and one or more amplifyingchambers (with the amplifying chambers in parallel or in series), amaster oscillator/power oscillator (MOPO) arrangement, a masteroscillator/power ring amplifier (MOPRA) arrangement, a poweroscillator/power amplifier (POPA) arrangement, or a solid state laserthat seeds one or more excimer or molecular fluorine amplifier oroscillator chambers, may be suitable. Other light source designs arepossible.

Referring again to FIG. 1, the EUV light source 20 may also include atarget material delivery system 24, for delivering portions (e.g.,droplets) of a target material into the interior of a EUV chamber 26 tothe irradiation region 28, where the droplets 102A, 102B will interactwith one or more light pulses 23, e.g., one or more pre-pulses andthereafter one or more irradiating pulses, to ultimately produce aplasma and generate an EUV emission 34. The target material may include,but is not necessarily limited to, a material that includes tin,lithium, xenon, etc., or combinations thereof. The EUV emitting element,e.g., tin, lithium, xenon, etc., may be in the form of liquid dropletsand/or solid particles contained within liquid droplets 102A, 102B orother forms as described elsewhere herein.

By way of example, the element tin may be used as pure tin, as a tincompound, e.g., SnBr4, SnBr2, SnH4, as a tin alloy, e.g., tin-galliumalloys, tin-indium alloys, tin-indium-gallium alloys, or a combinationthereof. Depending on the material used, the target material may bepresented to the irradiation region 28 at various temperatures includingroom temperature or near room temperature (e.g., tin alloys, SnBr4), atan elevated temperature, (e.g., pure tin) or at temperatures below roomtemperature, (e.g., SnH4), and in some cases, can be relativelyvolatile, e.g., SnBr4. More details concerning the use of thesematerials in an LPP EUV light source is provided in co-owned U.S. Pat.No. 7,465,946, issued Dec. 16, 2008, entitled ALTERNATIVE FUELS FOR EUVLIGHT SOURCE, the contents of which are hereby incorporated by referenceherein.

Referring further to FIG. 1, the EUV light source 20 includes acollector mirror 30. The collector mirror 30 is a near-normal incidencecollector mirror having a reflective surface in the form of a prolatespheroid (i.e., an ellipse rotated about its major axis). The actualshape and geometry can of course change depending on the size of thechamber and the location of focus. The collector mirror 30 can include agraded multi-layer coating in one or more embodiments. The gradedmulti-layer coating can include alternating layers of Molybdenum andSilicon, and in some cases one or more high temperature diffusionbarrier layers, smoothing layers, capping layers and/or etch stoplayers.

The collector mirror 30 also includes an aperture 32. The aperture 32allows the light pulses 23 generated by the light pulse generationsystem 22 to pass through to the irradiation region 28. The collectormirror 30 can be a prolate spheroid mirror that has a primary focus 31within or near the irradiation region 28 and an intermediate focus 40.The EUV light 34 is output at or near the intermediate focus 40 from theEUV light source 20 and input to a downstream device 42 utilizing EUVlight 34. By way of example, the downstream device 42 that receives theEUV light 34 can be an integrated circuit lithography tool (e.g., ascanner).

It is to be appreciated that other optics may be used in place of theprolate spheroid mirror 30 for collecting and directing EUV light 34 tothe intermediate focus 40 for subsequent delivery to a device utilizingthe EUV light. By way of example the collector mirror 30 can be aparabola rotated about its major axis. Alternatively, the collectormirror 30 can be configured to deliver a beam having a ring-shapedcross-section to the location of the intermediate focus 40 (e.g.,co-pending U.S. patent application Ser. No. 11/505,177, filed on Aug.16, 2006, entitled EUV OPTICS, the contents of which are herebyincorporated by reference).

The EUV light source 20 may also include a EUV controller 60. The EUVcontroller 60 can include a firing control system 65 for triggering oneor more lamps and/or laser devices in the light pulse generation system22 to thereby generate light pulses 23 for delivery into the chamber 26.

The EUV light source 20 may also include a target material positiondetection system including one or more target material imagers 70. Thetarget material imagers 70 can capture images using CCD's or otherimaging technologies and/or backlight stroboscopic illumination and/orlight curtains that provide an output indicative of the position and/ortiming of one or more target material droplets 102A, 102B relative tothe irradiation region 28. The imagers 70 are coupled to and output thetarget material location and timing data to a target material positiondetection feedback system 62. The target material position detectionfeedback system 62 can compute a target material position andtrajectory, from which a target material position error can be computed.The target material position error can be calculated on each portion oftarget material or an average basis (e.g., on a droplet by droplet basisor on average droplet data). The target material position error may thenbe provided as an input to the EUV controller 60. The EUV controller 60can provide a position, direction and/or timing correction signal to thelight pulse generation system 22 to control a source timing circuitand/or to control a beam position and shaping system to change thetrajectory and/or focal power or focal point of the light pulses 23being delivered to the irradiation region 28 in the chamber 26.

The EUV light source 20 can also include one or more EUV metrologyinstruments for measuring various properties of the EUV light generatedby the source 20. These properties may include, for example, intensity(e.g., total intensity or intensity within a particular spectral band),spectral bandwidth, polarization, beam position, pointing, etc. For theEUV light source 20, the instrument(s) may be configured to operatewhile the downstream tool, e.g., photolithography scanner, is on-line,e.g., by sampling a portion of the EUV output, e.g., using a pickoffmirror or sampling “uncollected” EUV light, and/or may operate while thedownstream tool, e.g., photolithography scanner, is off-line, forexample, by measuring the entire EUV output of the EUV light source 20.

The EUV light source 20 can also include a target material controlsystem 90, operable in response to a signal (which in someimplementations may include the target material position error describedabove, or some quantity derived there from) from the EUV controller 60,to e.g., modify the release point of the target material from a targetmaterial dispenser 92 and/or modify target material formation timing, tocorrect for position errors in the target material droplets 102A, 102Barriving at the desired irradiation region 28 and/or synchronize thegeneration of target material droplets 102A, 102B with the light pulsegeneration system 22.

FIG. 2A is a schematic of the components of a simplified target materialdispenser 92 that may be used in some or all of the embodimentsdescribed herein in accordance with embodiments of the disclosed subjectmatter. The target material dispenser 92 includes a conduit or reservoir94 holding a fluid form of the target material 96. The fluid targetmaterial 96 can be a liquid such as a molten metal (e.g., molten tin),under a pressure, P. The reservoir 94 includes an orifice 98 allowingthe pressurized fluid target material 96 to flow through the orifice 98establishing a continuous stream 100. The continuous stream 100subsequently breaks into a stream of droplets 102A, 102B. The targetmaterial dispenser 92 further includes a sub-system producing adisturbance in the fluid having an electro-actuatable element 104 thatis operable, coupled with the fluid target material 96 and/or theorifice 98 and a signal generator 106 driving the electro-actuatableelement 104.

More details regarding various target material dispenser 92configurations and their relative advantages may be found in co-pendingU.S. patent application Ser. No. 12/214,736, filed on Jun. 19, 2008,entitled SYSTEMS AND METHODS FOR TARGET MATERIAL DELIVERY IN A LASERPRODUCED PLASMA EUV LIGHT SOURCE; U.S. patent application Ser. No.11/827,803, filed on Jul. 13, 2007, entitled LASER PRODUCED PLASMA EUVLIGHT SOURCE HAVING A DROPLET STREAM PRODUCED USING A MODULATEDDISTURBANCE WAVE; co-pending U.S. patent application Ser. No.11/358,988, filed on Feb. 21, 2006, entitled LASER PRODUCED PLASMA EUVLIGHT SOURCE WITH PRE-PULSE; co-owned U.S. Pat. No. 7,405,416, issuedJul. 28, 2008, entitled METHOD AND APPARATUS FOR EUV PLASMA SOURCETARGET DELIVERY; and co-owned U.S. Pat. No. 7,372,056, issued May 13,2008, entitled LPP EUV PLASMA SOURCE MATERIAL TARGET DELIVERY SYSTEM;the contents of each of which are hereby incorporated by reference.

The droplets 102A, 102B are between about 20 μm and about 100 μm indiameter. The droplets 102A, 102B are produced by pressurizing targetmaterial 96 through the orifice 98. By way of example, the orifice 98can have a diameter of less than about 50 μm in one embodiment. Thedroplets 102A, 102B are launched at a velocity of about 20 to 70 m/s.Due to the high velocity of the droplets 102A, 102B, the droplet stay onthe nearly straight target material 209 and do not impinge on thecollector mirror 30, whether the droplets stream is produced inhorizontal, vertical, or some other orientation.

Not all the droplets 102A, 102B produced by the target materialdispenser 92 in continuous mode are used for plasma generation. If theEUV source works with a duty cycle of less than 100% a portion of thedroplets 102C will pass the irradiation region 28 and can be collectedthereafter in a first droplet catcher 210 or a second droplet catcher240. The droplets 102C captured in the first droplet catcher 210 and thesecond droplet catcher 240 can be accumulated as a quantity of targetmaterial 211, 242 in the respective droplet catchers. The accumulatedtarget material 211, 242 can be drained from the respective dropletcatchers through an outlet 244. A portion 236 of the unused droplets102C captured in the droplet catcher 210 can deflect inside the firstdroplet catcher. If the unused droplets 102C are allowed to impact theopposite wall of the EUV source chamber they will produce a large amountof fast moving fragments with broad spatial distribution. Significantportions of these fragments 231 will be deposited on the EUV collectormirror 30 and diagnostic ports and devices 70, thus affecting theirperformance.

Another source of the debris is the irradiation region 28. Whenirradiated with intense light pulses the droplets 102A, 102B are heatedon one side that results in rapid asymmetric material expansion and EUVlight emissions 230. As described above the EUV light emissions 230 arecollected in the collector mirror 30. As a result of the expansion asignificant amount of droplet material is accelerated in the directionaway from the light pulse 23 with velocities comparable to the velocityof the droplets 102A, 102B as they are output from the target materialdispenser 92. This material is traveling away from the irradiationregion 28 until it strikes some surface, at which point it can bereflected or backsplashed in various directions. The backsplashed targetmaterial 231 may be deposited on the collector mirror 30.

FIG. 2B is a more detailed schematic of some of the components in a EUVchamber 26 in accordance with embodiments of the disclosed subjectmatter. As described above, the target material dispenser 92 outputs astream of droplets 102A, 102B, however, not all of the droplets areirradiated (i.e., used) to generate the EUV 34. By way of example unuseddroplets 102C are not irradiated by the incoming light pulses 23.

FIG. 3A is a flowchart diagram that illustrates the method operations300 performed in generating EUV 34, in accordance with embodiments ofthe disclosed subject matter. The operations illustrated herein are byway of example, as it should be understood that some operations may havesub-operations and in other instances, certain operations describedherein may not be included in the illustrated operations. With this inmind, the method and operations 300 will now be described.

In an operation 302, a selected one 102C of a stream of droplets 102A,102B is delivered to an irradiation region 28. In an operation 304, alight pulse 23 is directed to the irradiation region 28 in the EUVchamber 26 at substantially the same time the selected droplet 102Barrives at the irradiation region. EUV light 34 is generated from theirradiated droplet 102B in an operation 306.

Directing the light pulse 23 to the irradiation region 28 includesadjusting the focal point of the light pulse to an optimum locationwhere the selected droplet 102B and the light pulse 23 meet. Optimizingthe focus of the light pulse 23 imparts maximum energy from the lightpulse 23 to the selected droplet. Adjusting the light pulse 23 tooptimize the intersection of the light pulse and the selected droplet102B is described in more detail below.

In an operation 308, the EUV from the irradiation region 28 is collectedby the collector mirror 30. The collector mirror 30 focuses the EUV 34to an intermediate location 40 in an operation 310 and in an operation312, the EUV 34 is output from the EUV chamber.

Aligning the Target Material with the Drive Laser in the X-Y Plane

The precise location of the irradiation of the selected droplet 102Brelative to the droplet itself and the drive laser is important as itdetermines the amount of energy imparted from the drive laser 23 to thedroplet 102B and the amount of EUV generated therefrom that thecollector mirror can collect and focus the collected EUV to theintermediate focal point 40. The downstream device 42 (e.g., scanner) ofthe EUV chamber 26 that consumes the EUV 34 determines the location ofthe intermediate point 40. The intermediate point 40 may vary slightlyfor many reasons including, for example, manufacturing and facility andchanges or movement of work pieces within the downstream device 42.

The precise location of the waist 320 relative to the selected targetmaterial droplet 102B is correspondingly adjusted or steered to optimizethe generation and collection of the EUV light 34.

FIGS. 3B-E are simplified schematics of the irradiation of a portion oftarget material, in accordance with embodiments of the disclosed subjectmatter. The focused drive laser 23 is focused to a narrow cross-sectionbeam referred to as a waist 320 where the drive laser is mostconcentrated. The optimum irradiation of the selected droplet 102Aoccurs at the waist 320 as the focused drive laser is most concentratedat the waist. As shown in FIG. 3B, the waist 320 is offset along the Zaxis from the selected target portion of material (i.e., droplet 102B)by a distance W (e.g., waist 320 is offset from the target material path394 by distance W). It should be noted that the offset distance W is notshown to scale and that W can be a relatively small distance such asless than about 5 μm to about 20 mm. Plasma 324A is generated as thefocused drive laser 23 irradiates the target material droplet 102B,however as the droplet is not aligned with the waist 320, only a firstportion 23A of the focused drive laser 23 impinges on and irradiates thedroplet while a second portion 23A′ of the focused drive laser 23 passesthe droplet. Thus, only the amount of energy in the first portion 23A ofthe focused drive laser 23 is applied to the droplet 102B. As a result,less than optimum energy is imparted from the focused drive laser 23 tothe droplet 102B and the resulting plasma 324A and EUV produced iscorrespondingly reduced.

FIG. 3C shows a side view of the irradiation of the selected portion oftarget material (i.e., droplet 102B) such that the target material path394 is across the view. As shown in FIG. 3C, the waist 320 is aligned tothe path 394 of the droplet 102B (e.g., W equals approximately zero).However, in FIG. 3C the droplet 102B is shown offset a distance V fromthe Z axis. The droplet 102B follows the target material path 394. Ifthe drive laser 23 uses the droplet 102B as a mirror for the opticalcavity then when the droplet is aligned with the drive laser 23, thedrive laser will also very nearly simultaneously arrive and thusirradiate the droplet. If the drive laser 23 does not use the droplet102B as a mirror for the optical cavity, then only a first portion 23Bof the focused drive laser 23 impinges on and irradiates the dropletwhile a second portion 23B′ of the focused drive laser 23 passes thedroplet. Thus, only the amount of energy in the first portion 23B of thefocused drive laser 23 is applied to the droplet 102B. As a result, lessthan optimum energy is imparted from the focused drive laser 23 to thedroplet 102B and the resulting plasma 324B and EUV produced iscorrespondingly reduced. The drive laser 23 can be aligned by steeringthe drive laser to the droplet 102B if the drive laser 23 and thedroplet are timed so that the droplet arrives at the waist 320 as thedrive laser 23 is output to the waist.

FIG. 3D shows a top view of the selected portion of target material(i.e., droplet 102B) such that the target material path 394 is notvisible as it passes perpendicular (e.g., into) the page. As shown inFIG. 3D, the droplet 102B is shown offset a distance H from the Z axisand a distance W′ from the waist 320. As the droplet 102B follows thetarget material path 394 it will not pass through the waist 320 andtherefore the droplet will not be irradiated optimally by the focuseddrive laser 23 as only a first portion 23C of the focused drive laser 23impinges on and irradiates the droplet 102B while a second portion 23C′of the focused drive laser 23 passes the droplet. Thus, only the amountof energy in the first portion 23C of the focused drive laser 23 isapplied to the droplet 102B. As a result, less than optimum energy isimparted from the focused drive laser 23 to the droplet 102B and theresulting plasma 324C and EUV produced is correspondingly reduced.

FIG. 3E shows a side view of the selected portion of target material(i.e., droplet 102B). As shown in FIG. 3E, the droplet 102B is shownaligned with the waist 320 of the focused drive laser 23. The droplet isalso aligned with the Z axis. A top view of the droplet 102B alignedwith the waist 320 of the focused drive laser 23 would also appear asshown in FIG. 3E except the target material path 394 would not be shownas described in FIG. 3D above. As the droplet 102B is aligned with boththe waist 320 and the Z axis, substantially the entire focused drivelaser 23 impinges on the droplet 102B and substantially none of thefocused drive laser 23 passes the droplet 102B (e.g., portion 23D′ issubstantially non-existent). Therefore, the droplet 102B will beirradiated optimally by the focused drive laser 23 and substantially allof the energy in the focused drive laser 23 is applied to the droplet102B. As a result, the resulting plasma 324D and EUV produced iscorrespondingly optimized.

FIGS. 4A and 4B are more detailed schematics of the light source 22, inaccordance with embodiments of the disclosed subject matter. FIG. 5A isa flowchart diagram that illustrates the method operations 500 performedin generating EUV 34, in accordance with embodiments of the disclosedsubject matter. The operations illustrated herein are by way of example,as it should be understood that some operations may have sub-operationsand in other instances, certain operations described herein may not beincluded in the illustrated operations. With this in mind, the methodand operations 500 will now be described.

Light source 22 includes a laser 415. The laser 415 can include one ormore laser generating and amplifying chambers 414, 416, 418 between anoutput window 404 and a beam reverser 412. The laser 415 can be a masteroscillator and power amplifier (MOPA) configuration or a no masteroscillator (NOMO) configuration. In an operation 505, the laser 415produces and amplifies a laser beam pulse 405A in the laser generatingand amplifying chambers 414, 416, 418. In an operation 510, the laser415 outputs a laser beam pulse 405B through the output window 404.

The laser beam pulse 405B is directed to the irradiation region 28 byreflecting surfaces or planes 464B, 452 and 454 in an operation 530. Byway of example, one or more of reflecting surfaces or planes 464B, 452and 454 can be a focusing of converging surface to cause the expandedlaser beam pulse 405C to converge and form the focused light 23 whichconverges to the waist 320 as shown in FIGS. 3B-E above. In optionaloperations not shown, directing the laser beam pulse to the irradiationregion can include inputting the output laser beam pulse 405B to a beamexpander 420. The beam expander 420 expands the pulse width of the laserbeam pulse to an expanded laser beam pulse that is output from the beamexpander 420. The expanded laser beam pulse can be directed toward theirradiation region 28 along a beam path 21 or beam transport system viareflecting surfaces or planes 422, 464B, 452 and 454. The reflectingsurfaces or planes 422, 464B, 452 and 454 can be mirrors or prisms orother suitable reflective media. The beam path 21 can be maintained at avacuum (e.g., less than about 1 mTorr) and can also include hydrogen gasbetween the output window 404 and the irradiation region 28.

One or more of reflecting surfaces or planes 464B, 452 and 454 can bemovable to steer the location of the waist 320 in the irradiation region28. By way of example actuator 456 can move reflecting surface or plane454 in one or more of directions 458A-D. The actuator 456 can be apiezoelectric actuator or a stepper motor controlled micro meter or anyother suitable type of actuator. Reflecting surface 452 can be anoff-axis parabolic mirror or a transmissive optic (e.g., a lens). Thislens can be translated along the optic axis to change the position ofthe waist of the focused laser. Reflecting surface 454 can be a flatmirror directing the converging drive laser 23 along the desired lightpath along the Z-axis in the EUV chamber. Reflecting surface 464B can bea flat mirror for reflecting the expanded pulse 405C toward the off-axisparabolic mirror 452. By way of example, the mirror 454 can receive thelaser 405C beam from off-axis parabolic focusing mirror 452 and steersthe converging, laser 23 to the waist 320 at the primary focus 31 of thecollector mirror 30.

Moving the reflecting surface or plane 454 in one or more of directions458A-D steers the waist 320 in the irradiation region 28 such that thewaist 320 is more precisely aligned with the target material. Thisimparts the maximum energy in the focused light 23 on the selecteddroplet 102B. Moving the reflecting surface or plane 454 in one or moreof directions 458A-D steers the waist 320 in an X-Y plane normal to theZ axis where the Z axis is the path of the focused drive laser 23 intoand through the EUV chamber 26. Moving the reflecting surface or plane454 in one or more of directions 458A-D can also steer the waist 320along the Z axis (e.g., −Z or +Z) either closer to or further away fromthe collector mirror 30.

The output window 404 can be any suitable output window. By way ofexample the output window 404 can be ZnSe or diamond output window. Theoutput window 404 can optionally include an optical power to focus thelaser 405B as it passes through the output window 404.

FIG. 5B is a flowchart diagram that illustrates the method operations550 performed in adjusting the position of the waist 320 relative to thetarget material, in accordance with embodiments of the disclosed subjectmatter. The operations illustrated herein are by way of example, as itshould be understood that some operations may have sub-operations and inother instances, certain operations described herein may not be includedin the illustrated operations. With this in mind, the method andoperations 550 will now be described.

Referring also to FIG. 4A, a portion 23A of light from the focused laserbeam 23 is reflected off of at least one preliminary droplet 102A in thedroplet stream following the target material path 394 in operation 552.The reflected light 23A is reflected back through the optical components454, 452, 464B 422, 420 toward light source 22 in operation 554.

The detector system 460 can be inline with the light path 21.Optionally, the detector system 460 can be off to one side of the lightpath 21 and the reflected light 23A can be reflected off the outputwindow 404 in an operation 556 as light 23B. The reflected light 23A or23B is directed toward the detector system 460 in an operation 560.

The detector system 460 can include a near field detector 466 and a farfield detector 464. The reflected light 23B is monitored in far fielddetector 464 and optionally in the near field detector 466 in operation564. In one configuration only one of the near field detector 466 andthe far field detector 464 may be included in the detector system 460.By way of example the detector system 460 can include only the far fielddetector 464 or alternatively, only the near field detector 466.

Light 23B reflected from the output window 404 to generate a near-fieldprofile on a near field detector 466. Light 23B reflected from theoutput window 404 can also or alternatively be used to generate afar-field profile on the far field detector 464. The near-field and/orfar-field profiles indicate the XY position of the at least onepreliminary droplet 102A relative to the waist 320 or Z axis of thedrive laser 23.

FIGS. 4C.1-4C.2 are far-field profile images 480A, 480B of the reflectedlight 23A, 23B reflected from preliminary droplet(s) 102A, in accordancewith embodiments of the disclosed subject matter. FIG. 4C.1 is an image480A of the reflected light 23A, 23B reflected from an alignedpreliminary droplet 102A. The aligned droplet image 102A′ is a fulldroplet in cross-sectional area and is substantially centered in theimage 480A. Due to the full droplet in cross-sectional area the amountof reflected light 23A or 23B is a maximum value and thus the focuseddrive laser 23 fully impinges on the droplet 102A.

FIG. 4C.2 is an image 480B of the reflected light 23A, 23B reflectedfrom a misaligned preliminary droplet 102A. The misaligned droplet image102A′ is not a full droplet in cross-sectional area and is substantiallyoffset to right (+X direction) in the image 480B. If less than the fulldroplet cross-section appears in the in image 480B, then the image ofthe droplet 102A is not centered and the droplet is less than optimallyaligned with the waist 320 of the focused drive laser 23. The deviationof the droplet image position from an optimum position provides thesignal used to steer the drive laser 23.

The detected location of the preliminary droplet(s) 102A can be comparedto a location of the waist 320 and/or Z axis of the focused drive laser23 based on the amount of reflected light 23A or the position of thereflected image 102A′ and a resulting difference value is converted intoan error signal by the controller 60. The error signal is used to adjust(e.g., tip/tilt in at least one of directions 458A-D) mirror 454 usingactuator 456. By way of example, the tip/tilt adjustment can be made asmultiple droplets are irradiated by the light 23 until the error signalis a null.

The controller 60 detects one or both the near-field and far-fieldimages of the reflected light 23A or 23B in an operation 566. In anoperation 570, the controller 60 adjusts the actuator 456 to adjust theposition of the mirror 454 and thereby steer the precise location of thewaist 320 relative to the waist 320 and/or Z axis of the focused drivelaser 23. In an optional or alternative operation 572, the controller 60adjusts the release of at least one subsequent droplet(s) 102B from thedroplet generator 92 and/or adjusts a timing of the drive laser pulse23. The adjustment can include adjusting the timing of the release ofthe subsequent droplet and can include adjusting the direction of thetarget material path 394.

In an operation 574, at least one subsequent droplet 102B arrives at thewaist 320 of the focused drive laser 23 and the droplet 102B to impartthe maximum amount of energy from the focused light 23 to the droplet102B thus irradiating the droplet 102B and producing an optimum amountof EUV light 34.

A first pulse of the focused light 23 can have a lower energy than asecond pulse of the focused light 23 where the first pulse of thefocused light 23 irradiates the preliminary droplet(s) 102A to determinea location of the preliminary droplet(s) 102A. The second pulse of thefocused light 23 is directed at the subsequent droplet(s) 102B toirradiate the subsequent droplet(s). The method and operations 550 cancontinuously repeat for subsequent droplets.

The light source 22 can be a CO2 laser. The light source 22 can be aNOMO configuration (e.g. no master oscillator is used) and an opticalcavity is established between the beam reverser 412 and a droplet 102A,102B when the droplet reaches the Z-axis in the EUV chamber 26. Anamplifier 415 can include a chain of amplifier chambers 414, 416, 418,each chamber having its own gain media and excitation source to amplifylight in the cavity.

Light 23A reflected from the first droplet 102A is directed toward thebeam reverser 412 and is at least partially reflected by the output 404window as reflected light 23B. The output 404 window can be placed at anangle to the beam path 21. Placing the window at a slight angle can alsoprevent direct reflections along the drive laser beam path as anyreflections from light along the beam path would be directed out of thebeam path. By way of example the output 404 window can be placed at ornear the Brewster's angle. At an ideal Brewster's angle to the path ofthe laser, the output window 404 is completely transparent and passes100% of the light. Typically the output window absorbs or reflects up toabout 2% of the light and passes the remaining light (about 98%).

On one side of the output window 404 is a CO2 gain media. The oppositeside of the window 404 is in fluid communication with the irradiationregion 28 via the beam path 21. The beam path 21 is maintained at avacuum and in at least one embodiment can include hydrogen at a pressureof less than about 1 mTorr.

FIG. 4D is a simplified schematic of the target material 394, inaccordance with embodiments of the disclosed subject matter. The targetmaterial path 394 can be at an angle θ relative to the X-Y plane normalto the Z-axis, in accordance with embodiments of the disclosed subjectmatter. θ can be any angle from about between about 90 degrees and 0degrees relative to the X-Y plane. The X-Y plane is perpendicular to theZ axis. The X and Y axes correspond to angular components of the targetmaterial path 394.

EUV Z Axis Optimization

The above systems and methods describe the alignment for the targetmaterial and the drive laser for optimum calculated result for theoptimum EUV output. However the above described systems and methods donot accurately compensate for dynamic changes in the EUV chamber 26 andmore specifically the dynamic conditions occurring at the primary focus31 of the collector mirror 30 during the production of the plasma andthe resulting EUV 34.

Referring again to FIG. 4B above, the filter 484 filters out of bandlight (e.g., visible light) and passes EUV to detector 483. The detector483 couples a signal corresponding to the amount of detected EUV to thecontroller 60. The controller 60 analyzes the amount of detected EUV andsends a correction signal to the drive laser focusing system 402. Theanalysis of the amount of detected EUV includes comparing the detectedEUV signal to another EUV signal level such as a previous EUV signal ora desired EUV signal. The filter 484 can be a thin film filter such as athin film of zirconium having a thickness of about 0.2 micron as such athin film is opaque to visible light but substantially fullytransmissive to EUV. The detector 485 can be any suitable EUV detector.By way of example the detector 485 can be a broad spectrum photodiode.The detector 485 can be a broad spectrum photodiode having a relativelylarge area (e.g., an area of less than about 50 square millimeters tomore than about 100 square millimeters).

Common stage 482 includes an actuator and allows the mirrors 452, 454 tobe moved as a single stage in direction 458A and 458B. This allows thewaist 320 of the focused drive laser 23 to be translated along theZ-axis having the same focal length and also adjusting the distance ofwaist 320 from the collector mirror 30 along the Z-axis. Used incombination, the common stage 482 and the actuator 456 allows the waist320 of the drive laser to be selectively translated within a range ofvalues in the X-Y plane and at different distances from the collectormirror 30 along the Z-axis. By way of example the common stage 482 andthe actuator 456 allows the waist 320 to be aligned with the primaryfocus 31 of the collector mirror 30.

FIGS. 6A, 7A and 8A are simplified close up views of the irradiationregion 28 in accordance with embodiments of the disclosed subjectmatter. FIGS. 6B, 7B and 8B are graphical representations of multiplefocused light pulses 23 corresponding to FIGS. 6A, 7A and 8A,respectively, in accordance with embodiments of the disclosed subjectmatter. FIGS. 6C, 7C and 8C are graphical representations of theresulting multiple EUV pulses 34 corresponding to the multiple focusedlight pulses in FIGS. 6B, 7B and 8B, respectively, in accordance withembodiments of the disclosed subject matter. FIGS. 6D, 7D and 8D aregraphical representations of corresponding integrals of the multipleresulting EUV pulses 34 corresponding to FIGS. 6C, 7C and 8C,respectively, in accordance with embodiments of the disclosed subjectmatter.

FIG. 9 is a flowchart diagram that illustrates the method operations 900performed in adjusting the position of the waist 320 relative to thetarget material to optimize EUV 34 output, in accordance withembodiments of the disclosed subject matter. The operations illustratedherein are by way of example, as it should be understood that someoperations may have sub-operations and in other instances, certainoperations described herein may not be included in the illustratedoperations. With this in mind, the method and operations 900 will now bedescribed.

In an operation 905, a target material 102B is placed in the waist 320of the focused laser 23. A focused laser pulse 23 is directed on thetarget material 102B in an operation 910.

In an operation 915, the EUV output pulse corresponding to focused laserpulse 23 in operation 910 is measured (e.g., by detector 483 or via afeedback signal from the downstream device 42). In an operation 920,operations 905-915 are repeated multiple iterations of focused laserpulses and subsequent portions of target material 102B whileincrementing the location of the subsequent portions of target materialin the −Z direction relative to the waist 320 until a selected timeinterval expires. By way of example, a 1 ms time interval can beselected and however many laser pulses and target material portions(e.g., droplets in one embodiment) 102B can be delivered to the waist320 of the focused laser pulses.

In an operation 925, an integral of multiple iterations during selectedtime interval is determined. The area under the curve of the integralcorresponds to the EUV output 34 over the selected time interval.

In an operation 930, the recorded EUV pulses across the multipleiterations during the selected time interval are examined to determinewhich pulse or pulses have the greatest peak EUV. If the greatest peakEUV occurs in the first one of multiple iterations then the operationscontinue in an operation 945. In operation 945, the controller adjuststarget material position in +Z direction relative to the waist 320 ofthe focused laser 23.

In operation 930, if the greatest peak(s) EUV do not occur in the firstone of multiple iterations then the operations continue in an operation935. In operation 935, the recorded EUV pulses across the multipleiterations during selected time interval are examined to determine whichpulse or pulses have the greatest peak EUV. If the greatest peak EUVoccurs in the last one of multiple iterations then the operationscontinue in an operation 950. In operation 950, the controller adjuststarget material position in −Z direction relative to the waist 320 ofthe focused laser 23.

In operation 935, if the greatest peak(s) EUV do not occur in the lastportion of multiple iterations then the operations continue in anoperation 940. In operation 940 repeat operations 905-935 to generateEUV at optimum level until the EUV 34 is no longer needed and the methodoperations can end.

Referring to FIGS. 6A-6D, the droplet is in the +Z position relative tothe waist 320 of the focused drive laser 23. The tapering EUV outputindicates droplet position is slightly offset in the −Z direction fromthe optimum location in or near waist 320 of the focused laser 23. As aresult the output EUV pulses 34 shown in FIG. 6C are less than optimumhaving a high initial energy that quickly tapers downward. The focusingoptics move in −Z direction or droplets in +Z direction.

It should be understood that the relative positions of the targetmaterial 102B and the waist 320 of the focused laser 23 are somewhatexaggerated in the FIGS. 6A-8A so as to emphasize the relative movement.The actual change in location can be less than about a diameter of thetarget material 102B. Further the optimum position may be slightlyoffset on the Z axis from a center of the waist 320 of the focused laser23. The waist 320 can have a width wider than the target material 102B.

Referring to FIGS. 7A-7D, the droplet is in the −Z position relative tothe waist 320 of the focused drive laser 23. The increasing EUV outputindicates droplet position is beyond optimum focal point. As a resultthe output EUV pulse 34 shown in FIGS. 7C and 7D is less than optimumhaving a low initial energy that quickly tapers upward to an abruptlyterminated peak. Move optics in +Z direction or droplets in −Zdirection.

Referring to FIGS. 8A-8D, the droplet is in the optimum position (e.g.,desired focal point). As a result the output EUV pulse 34 shown in FIGS.8C and 8D is optimized having more consistent energy (e.g., fewer peaksor steep slopes) throughout the pulse as compared to either of thoseshown in FIGS. 6C and 6D or FIGS. 7C and 7D. The more consistent energyprovides more consistent results in the downstream device 42.

FIG. 10 is a block diagram of an integrated system 1000 including theEUV chamber 26, in accordance with embodiments of the disclosed subjectmatter. The integrated system 1000 includes the EUV chamber 26, thelight pulse generation system 22, the device 42 utilizing output EUVlight 34, and an integrated system controller 1010 coupled to the EUVchamber, the light pulse generation system and the device utilizingoutput EUV light. The integrated system controller 1010 includes or iscoupled to (e.g., via a wired or wireless network 1012) a user interface1014. The user interface 1014 provides user readable outputs andindications and can receive user inputs and provides user access to theintegrated system controller 1010.

The integrated system controller 1010 can include a special purposecomputer or a general purpose computer. The integrated system controller1010 can execute computer programs 1016 to monitor, control and collectand store data 1018 (e.g., performance history, analysis of performanceor defects, operator logs, and history, etc.) for the EUV chamber 26,the light pulse generation system 22 and the device 42. By way ofexample, the integrated system controller 1010 can adjust the operationsof the EUV chamber 26, the light pulse generation system 22 and/or thedevice 42 and/or the components therein (e.g., the target materialdispenser 92, etc.) if data collected dictates an adjustment to theoperation thereof.

One embodiment provides an extreme ultraviolet light system including adrive laser system, an extreme ultraviolet light chamber, a drive lasersteering device, a detection system and a controller. The extremeultraviolet light chamber including a extreme ultraviolet lightcollector and a target material dispenser including a target materialoutlet capable of outputting multiple portions of target material alonga target material path. The target material outlet is adjustable. Thedetection system includes at least one detector directed to detect areflection of the drive laser reflected from the first one of theportions of target material. The controller is coupled to the targetmaterial dispenser, the detector system and the drive laser steeringdevice. The controller includes logic for detecting a location of afirst one of the portions of target material from a first lightreflected from the first target material and logic for adjusting thetarget material dispenser outlet to output a subsequent one of theportions of target material to a waist of the focused drive laser.

The drive laser can be aligned with a light path between the drive laserand the first one of the portions of the target material. The detectionsystem can be in line with the light path, and the reflection of thedrive laser reflected off of the first one of the portions of the targetmaterial is reflected along the light path toward the drive laser. Thedrive laser system can include an output window and the detection systemmay not be in line with the light path and the reflection of the drivelaser reflected off of the first one of the portions of the targetmaterial can be reflected along the light path toward the drive laseroutput window and the reflection of the drive laser is further reflectedoff of the output window and toward the detection system.

The system can also include logic for irradiating the second one of theportions of target material with the drive laser. The drive lasersteering device can include at least one reflecting surface. The drivelaser steering device can further include at least one actuator coupledto the at least one reflecting surface.

The detector directed to detect light reflected from the first targetmaterial can include a near field detector and/or a far field detector.The drive laser system can be a CO2 laser. The drive laser system caninclude a master oscillator power amplifier configuration laser. Thedrive laser system can include a multi stage amplifier. The drive lasersystem can include a ZnSe or a diamond output window or any othersuitable output window.

The waist of the focused drive laser is in an XY plane normal to a lightpath of the drive laser along a Z axis. The portions of target materialare output along a target material path and the target material path canform an angle to the XY plane.

Another embodiment provides a method of generating an extremeultraviolet light. The method includes irradiating a first portion oneof multiple portions of a target material with a drive laser, detectinga first light pulse reflected from the first portion of the targetmaterial, determining a location of the first portion of the targetmaterial, adjusting a location of a second one of the portions of thetarget material to a waist of a focused drive laser, irradiating thesecond one of the of portions of the target material with the drivelaser.

Detecting the first light pulse reflected from the first portion of thetarget material can include detecting the first light pulse reflectedfrom an output window of the drive laser. Detecting the first lightpulse reflected from the first portion of the target material caninclude determining a near field profile of the first portion of thetarget material. Detecting the first light pulse reflected from thefirst portion of the target material can include determining a far fieldprofile of the first portion of the target material. Adjusting the waistof the focused drive laser includes adjusting a position of at least onereflecting surface of the drive laser.

Yet another embodiment provides a method of optimizing an extremeultraviolet light output. The method includes determining an amount ofeach one of a first set of EUV output pulses during a selected timeinterval including for each one of the first set of EUV output pulsesincluding placing a corresponding one of a first set of portions oftarget material target material in a waist of the focused drive laser,directing a focused drive laser pulse on the corresponding one of thefirst set of portions of target material, measuring an amount of acorresponding EUV output pulse, and recording the measured correspondingEUV output pulse quantity. Each one of the first set of EUV outputpulses is analyzed and a target material position is adjusted in the +Zdirection relative to the waist of the focused laser when the greatestpeak EUV amount occurs in a first occurring one of the first pluralityof EUV output pulses and the target material position is adjusted in −Zdirection relative to the waist of the focused laser when the greatestpeak EUV amount occurs in a last occurring one of the first plurality ofEUV output pulses. The method of can also include determining anintegral of the first set of EUV output pulses during the selected timeinterval.

With the above embodiments in mind, it should be understood that theinvention may employ various computer-implemented operations involvingdata stored in computer systems. These operations are those requiringphysical manipulation of physical quantities. Usually, though notnecessarily, these quantities take the form of electrical or magneticsignals capable of being stored, transferred, combined, compared, andotherwise manipulated. Further, the manipulations performed are oftenreferred to in terms, such as producing, identifying, determining, orcomparing.

Any of the operations described herein that form part of the inventionare useful machine operations. The invention also relates to a device oran apparatus for performing these operations. The apparatus may bespecially constructed for the required purpose, such as a specialpurpose computer. When defined as a special purpose computer, thecomputer can also perform other processing, program execution orroutines that are not part of the special purpose, while still beingcapable of operating for the special purpose. Alternatively, theoperations may be processed by a general purpose computer selectivelyactivated or configured by one or more computer programs stored in thecomputer memory, cache, or obtained over a network. When data isobtained over a network the data maybe processed by other computers onthe network, e.g., a cloud of computing resources.

The embodiments of the present invention can also be defined as amachine that transforms data from one state to another state. Thetransformed data can be saved to storage and then manipulated by aprocessor. The processor thus transforms the data from one thing toanother. Still further, the methods can be processed by one or moremachines or processors that can be connected over a network. Eachmachine can transform data from one state or thing to another, and canalso process data, save data to storage, transmit data over a network,display the result, or communicate the result to another machine.

The invention may be practiced with other computer system configurationsincluding hand-held devices, microprocessor systems,microprocessor-based or programmable consumer electronics,minicomputers, mainframe computers and the like. The invention may alsobe practiced in distributing computing environments where tasks areperformed by remote processing devices that are linked through anetwork.

The invention can also be embodied as computer readable code on acomputer readable medium. The computer readable medium is any datastorage device that can store data, which can thereafter be read by acomputer system. Examples of the computer readable medium include harddrives, network attached storage (NAS), read-only memory, random-accessmemory, CD-ROMs, CD-Rs, CD-RWs, DVDs, Flash, magnetic tapes, and otheroptical and non-optical data storage devices. The computer readablemedium can also be distributed over a network coupled computer systemsso that the computer readable code is stored and executed in adistributed fashion.

It will be further appreciated that the instructions represented by theoperations in the above figures are not required to be performed in theorder illustrated, and that all the processing represented by theoperations may not be necessary to practice the invention.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. Accordingly, the present embodiments are to beconsidered as illustrative and not restrictive, and the invention is notto be limited to the details given herein, but may be modified withinthe scope and equivalents of the appended claims.

What is claimed is:
 1. A method of generating an extreme ultravioletlight comprising: irradiating a reflective surface on a first one of aplurality of portions of a target material with a first drive laserpulse, wherein the first drive laser pulse passes through an aperture inan extreme ultraviolet collector to the reflective surface of the firstportion of the target material; reflecting the first drive laser pulseoff the reflective surface of the first portion of the target materialwherein the reflected first drive laser pulse passes through theaperture in the extreme ultraviolet collector to an output window of adrive laser; reflecting the reflected first drive laser pulse off of theoutput window of the drive laser to a detector; detecting the reflectedfirst drive laser pulse in the detector; determining a location of thefirst portion of the target material based on the detected reflection;outputting the location of the first portion of the target material to acontroller, the controller including logic on a computer readable mediumfor adjusting a location of a second one of the plurality of portions ofthe target material to a waist of a focused drive laser; and irradiatingthe second one of the plurality of portions of the target material witha second drive laser pulse.
 2. The method of claim 1, wherein thereflecting surface of the first portion of target material faces theextreme ultraviolet collector and the reflected first drive laser pulseis reflected through the aperture in the extreme ultraviolet collectorto the output window of the drive laser system.
 3. The method of claim1, wherein detecting the reflected first drive laser pulse from thefirst portion of the target material includes determining at least oneof a near field profile of the first portion of the target material or afar field profile of the first portion of the target material.
 4. Themethod of claim 1, wherein adjusting the location of the second one ofthe plurality of portions of the target material to the waist of thefocused drive laser includes translating the waist of the focused drivelaser including adjusting a position of at least one reflecting surfaceof the drive laser.
 5. The method of claim 4, wherein adjusting theposition of at least one reflecting surface of the drive laser includesadjusting a target material dispenser outlet to output the second one ofthe plurality of portions of target material to the waist of the focuseddrive laser.
 6. The method of claim 4, wherein adjusting the position ofat least one reflecting surface of the drive laser includes translatingthe location of the waist of the focused drive laser.
 7. The method ofclaim 4, wherein translating the location of the waist of the focuseddrive laser includes outputting a steering signal from the controller toat least one actuator coupled to a drive laser steering device includingat least one reflecting surface.
 8. The method of claim 1, wherein thewaist of the focused drive laser is in an XY plane normal to a lightpath of the drive laser along a Z axis.
 9. The method of claim 8,wherein the plurality of portions of target material are output along atarget material path and wherein the target material path forms an anglebetween more than 0 degrees and less than 90 degrees relative to the XYplane.
 10. The method of claim 1, wherein the drive laser is alignedwith a light path between the drive laser and the first one of theplurality of portions of the target material.
 11. The method of claim10, wherein the detection system is in line with at least a portion ofthe light path, and wherein the reflected drive laser pulse is directedalong the light path toward the drive laser output window.
 12. Themethod of claim 1, wherein the drive laser system includes a masteroscillator power amplifier configuration laser including at least oneamplifier stage.
 13. The method of claim 1, wherein the drive laserincludes a CO2 laser.
 14. A method of steering a drive laser comprising:dispensing a first one of a plurality of portions of target materialalong a target material path, wherein the plurality of portions oftarget material are dispensed from a target material dispenser having anadjustable target material outlet; irradiating a reflective surface onthe first portion of target material with a first drive laser pulse;reflecting the first drive laser pulse off the reflective surface of thefirst portion of the target material wherein the reflected first drivelaser pulse passes through an aperture in an extreme ultravioletcollector to an output window of a drive laser; reflecting the reflectedfirst drive laser pulse off of the output window of the drive laser to adetector; detecting the reflected first drive laser pulse in thedetector; determining a location of the first portion of the targetmaterial based on the detected reflection; outputting the location ofthe first portion of the target material to a controller, the controllerincluding logic on a computer readable medium for adjusting a locationof a second one of the plurality of portions of the target material to awaist of a focused drive laser; and irradiating the second one of theplurality of portions of the target material with a second drive laserpulse.
 15. The method of claim 14, further comprising a drive lasersteering device disposed to direct the drive laser through the aperture,the drive laser steering device including at least one actuator coupledto the controller.
 16. The method of claim 14, wherein the detectorincludes more than one detector.
 17. The method of claim 14, wherein thedetector is directed toward the output window of the drive laser systemto detect a reflection of a first drive laser pulse reflected from areflecting surface of the first portion of target material.
 18. Themethod of claim 14, wherein the reflecting surface of the first portionof target material faces the extreme ultraviolet collector and thereflected first drive laser pulse is reflected through the aperture inthe extreme ultraviolet collector to the output window of the drivelaser system.